A resist composition is a patter formation material in which an acid is generated in the exposed area upon irradiation of radiation, for example, a far ultraviolet ray, and solubility in a developing solution between the exposed area with the radiation and the unexposed area is differentiated by a reaction using the acid as a catalyst, whereby a pattern is formed on a substrate.
With respect to the resist composition, for instance, an acid-generator having a specific structure in which a sulfur atom (cation) is substituted with a fluorine-substituted alkyl group is described in Patent Document 1 (WO 02/39186).
Also, an acid-generator containing, for example, a halogen atom, a trifluoromethyl group or the like in both a cation and an anion is described in Patent Document (JP-A-2000-258902 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)).
However, it has been desired for hitherto known resist compositions to further improve line edge roughness. The term “line edge roughness” used herein means a phenomenon wherein edges of top and bottom of a line pattern of resist irregularly fluctuate in the direction vertical to the line due to the characteristics of resist and the edges are seen uneven, when the pattern is observed from just above.
Patent Document 1: WO 02/39186
Patent Document 2: JP-A-2000-258902